The American driver John Fitch, who has died aged 95, first made his mark by winning the 1951 Buenos Aires Grand Prix for sports cars. He raced competitively for the next 15 years, after what he referred to as his "hero impulse" had taken him into the air during the second world war and to sea in yachts. A survivor of motor racing's worst accident, he also played a significant role in the development of motoring safety measures.

In Buenos Aires, driving an Allard-Cadillac, he caught the eye of his compatriot Briggs Cunningham, a millionaire at the centre of a wealthy young east-coast social set with the resources to pursue any sporting whim he fancied. Fitch joined Cunningham's multicar team, and did much to help Cunningham pursue his dream of winning the Le Mans 24-hour event, though the ambition was never achieved. In 1951, Cunningham's C2-R, driven by Fitch and Phil Walters, held second position for several hours before a minor problem forced it to drop out. The following year, in a Cunningham CR-5, the pair came third.

At the start of 1955 Fitch was signed up by the Mercedes team manager, Alfred Neubauer. At Le Mans that June, the Mercedes-Benz 300 SLR that Fitch was sharing with the French driver Pierre Levegh scythed into the crowd opposite the pits, killing more than 80 onlookers in a fireball. Levegh, aged 49 and out of his depth at the wheel of such a high-performance machine, also perished in the accident, leaving Fitch utterly outraged, if out of step, at the apparent determination of the Mercedes team management to continue competing. The race was not stopped because if spectators left, then ambulances would have been unable to arrive.

Only after protracted talks at the Mercedes headquarters in Stuttgart did word come in the small hours of Sunday morning that their remaining cars should be withdrawn. The company eventually abandoned circuit racing until the 1980s, though Fitch did share the winning 300 SL with Stirling Moss in the RAC Tourist Trophy on the street circuit at Dundrod, Co Antrim, in September 1955.

Fitch established a reputation as an accomplished semi-professional. While he might have not have ranked among the quickest, there was no doubting his bravery or commitment.

After returning to the US in 1956 he became involved in Chevrolet's sports car-racing programme on an informal basis and later became hands-on in the development and management of the Lime Rock circuit, Connecticut, which was always in demand for road- and race-car-testing purposes.

Born in Indianapolis, Indiana, John followed his great-great-grandfather, the inventor of the steamboat, by becoming interested in its engineering when young. His stepfather was president of the Stutz Motor company, whose products combined fashionable styling with cutting-edge automotive engineering. John attended the Kentucky Military Institute and then studied civil engineering at Lehigh University, Pennsylvania, for a year.

In 1941 he volunteered for service with the US Army Air Corps, and by 1944 had been promoted to P-51 Mustang pilot and then moved over to fly the A20 Havoc fighter. It was in the cockpit of a Mustang that he posted his most memorable achievement, the downing of a Messerschmidt Me 262, the first jet fighter. However, shortly afterwards he was shot down trying to strafe a freight train and spent the last three months of the conflict as a prisoner of war.

Once back in the US, he became part of the social scene in Palm Beach, Florida, and raced yachts till he took to autosport. His crash experience motivated him to develop various safety mechanisms: the Fitch Inertial Barrier, a set of yellow plastic barrels containing varying amounts of sand, is estimated to have saved more than 17,000 lives on US highways.

Fitch and his wife, Elizabeth, eventually settled at his 18th-century ancestral home in Connecticut. She predeceased him in 2009, and he is survived by three sons.

•John Cooper Fitch, racing driver, born 4 August 1917; died 31 October 2012